Levernut. 22 bhn is too hard for the longer ranges as it won't expand when velocity drops a couple hundred fps from your max load, and if it does expand, it really doesn't expand but only breaks down leaving a blunt shank, which is very effective, never the less. You'll need an alloy hardness of about 14 bhn for optimum expansion, and especially at the longer ranges.
You didn't mention the type of lube you are using. I'm suspecting that you are using something other than LBT lube, as 2400 fps is normally quite easy to get with 14 bhn bullets and the slower powders. Accuracy will probably not be better than 1 1/2 to 2 inches at 100 yards, but that's adaquate for chest hits on anything from coyotes up out to 300 yards. The reason tighter groups are hard to get with the easy expanding alloy is just that. The bullets expand on the back end during takeoff, which deforms them a bit to much for top accuracy.
When I first started to really get 30-06 performance with cast I was running 165 - 170 grain bullets at 2850 fps, and groups were 3 inches and sometimes a bit over. This with 20 plus shanks and softnoses. But with this accuracy I never missed out to 400 plus yards, and feral dogs caught more of my bullets than did edible game.
One year I got unto a herd of deer in a box canyon, about 125 yards across, and racked off three shots rapidly, taking three deer. During the following week of ringing ears I decided I would never use a rifle that made my ears ring again, and I haven't. That's the main reason I settled on 2400 fps velocity from the 30-06. It is not nasty loud yet I can hit with precision out to 525 yards, which was my longest shot on a feral dog, which was trotting, by the way, and dropped in his tracks with the essential organs in his chest creamed. If it sounds like I'm bragging, this will undo that issue. I had just missed him at 35 yards, running but not hard. I ran to the top of a hill and when he topped out on the far side of the canyon he had just crossed, took the above shot, offhand. He was a chicken thief who's time was up.
Almost any rifle is good with cast when the right bullets are used, and I'm not stuck on the 30-06, except that it gives up nothing. I've used a broad spectrum of rifles from 32-20, 7 TCU, 357, 44 mag, 30-30, 308 30-06 and 458 Win mag. They all work great within their limits. I took a mature bull elk with the little 7 TCU and 130 gr softnose bullet started at 2450 fps. The bullet broke his shoulder bone (not joint) and severed his spine, then exited his off shoulder.
The key to good performance with cast is selecting the right bullet for the cartridge of interest, making it expand if the caliber is small, and not stretching it's working range when using it.
My wifes favorite cast bullet rifle is the Marlin 357 mag with 180 gr FN started at 1800 fps, which she has taken coyote, deer and elk with it. She views a gun as a tool, only, and calls this gun, 'the quiet gun'. Recoil is pleasant even for her 120 pound frame, the blast doesn't hurt and effective range is about 200 yards without allowing for trajectory on big game.
